Maintenance Scheduling, Equipment reliability11th April 2021
Schedule repair jobs
During operations, LRUs that need repair are released to the repair shop and need to be repaired within the agreed planned lead time. This naturally leads to due-dates for repair jobs. The repair job scheduling function is to schedule the repair jobs subject to the resource constraints which are a consequence of the capacity dimensioning decision. Within these constraints, specific resources are assigned to specific repair jobs for specific periods in time so as to minimize the repair job tardiness. Additionally, the repair shop may batch repair jobs to use resources more efficiently by reducing set-up time and costs associated with using certain resources.
Maintenance planning can be defined as an end-to-end process that identifies and addresses any possible issues ahead of time. This involves identifying the parts and tools necessary for jobs and making sure they’re available and laid out in the appropriate areas, having a planner write out instructions on how to complete a job, and even determining and gathering the necessary parts and/or tools before a job is assigned. Maintenance planning also includes tasks related to parts like:
- Handling reserve parts
- Ordering nonstock parts
- Staging parts
- Illustrating parts
- Managing breakdowns and vendor lists
- Quality assurance (QA) and quality control (QC)
Maintenance planning should define the “what,” “why” and “how.” This means specifying what work needs to be done with what materials, tools and equipment; why a particular action was chosen (why a valve is being replaced instead of a seat); and how the work should be completed.
Maintenance scheduling refers to the timing of planned work, when the work should be done and who should perform it. It offers details of “when” and “who.” Scheduling is meant to:
- Schedule the maximum amount of work with the available resources
- Schedule according to the highest priority work orders
- Schedule the maximum number of preventive maintenance jobs when necessary
- Minimize the use of contract and outside resources by effectively using internal labor
When implemented together, maintenance planning and scheduling should have a significant benefit in multiple areas of your organization. These can include:
- Help with budgeting by controlling resources associated with maintenance
- A reduction in equipment downtime
- A reduction in spare parts
- Improved workflow
- Improved efficiency by minimizing the movement of resources between areas
- Job plans are needed for scheduling: Job plans should include the number of technicians required, the minimum skill level, work hours per skill level and information on job duration. Maintenance needs this information to schedule work, and job plans provide it in an efficient way. Does the job require welding? How many welders are needed? How many assistants does the engineer require? Asking questions like these during the creation of job plans helps determine scheduling requirements.
- Schedules and job priorities are important: The weekly schedule and the priorities that help determine this schedule are essential to improving productivity. Weekly scheduling frees up crew supervisors to focus on the current week without worrying about the backlog. Maintenance and operations use the weekly schedule for coordinating their tasks in advance, so it’s critical to properly determine the priority levels of new work orders to see if they should become part of the daily or weekly schedule.
Prioritizing advanced scheduling helps make sure sufficient workloads are assigned, which increases productivity and ensures critical work orders are completed first.
- Schedule based on the projected highest skills available: This principle states that a scheduler should develop a one-week schedule for each crew based on the available technician hours, the highest skill levels available, job priorities and details from the job plans. Schedulers should select a week’s worth of work from the plant backlog by using information on priority and job plan details. They should then use a forecast of the maximum capabilities of the technician crew for the coming week. After several weeks have passed, technicians should have a better idea about the amount of work they’re responsible for in a given week and become more productive.
- Schedule for every available work hour: Bringing the previous principles together, this guideline details how much work to schedule. The scheduler should assign work plans for the technicians to complete a task during the following week for 100 percent of the forecasted hours. So, if a crew has 800 labor hours available, the scheduler would give them 800 hours’ worth of work. Scheduling for 100 percent of the forecasted work hours prevents over- and under-scheduling.
- Daily work is handled by the crew leader: The crew leader or supervisor should develop a daily schedule based on the one-week schedule, current job progress and any new high-priority jobs that may arise. The supervisor should assign daily work to technicians based on skill level and work order requirements. In addition to the current days’ workload, the supervisor should handle emergencies and reschedule assignments as needed. Daily scheduling is almost always fluid thanks to the progress of the work being performed. This makes it difficult to schedule precise job times very far in advance. Inaccuracy of individual time estimates and reactive maintenance are the two biggest factors contributing to this issue.
- Measure performance with schedule compliance: Scheduling success is measured by the adherence to the one-week schedule and its effectiveness. Wrench time is the ultimate measure of workforce efficiency and planning and scheduling effectiveness. Planning work before assigning it reduces unnecessary delays, while scheduled work reduces delays between jobs.
Implement Maintenance Planning and Scheduling
Phase 1: Setup: This phase encompasses all the steps needed to ensure your organization is onboard with implementing maintenance planning and scheduling. You should have made your case to leadership by exposing the issue of low productivity, explaining how planning and scheduling can help solve that issue, calculating the value of productivity improvement, and presenting the results in the form of return on investment (ROI).
Phase 2: Define and analyze the situation: Phase two involves your team looking at your current situation and identifying problems currently faced in maintenance execution. During this phase, you should have representation from all levels of the maintenance process technicians, key managers or supervisors, and even representatives from procurement, finance and the warehouse. This workshop-like environment should outline the current maintenance planning and scheduling process.
Phase 3: Develop and prepare for delivery: Phase three involves planners and supervisors working to establish supporting documentation and process maps as well as defining in detail new processes, roles and responsibilities. You should also make any necessary changes to your computerized maintenance management system (CMMS) and develop training and coaching programs. Conducting a single overview training session followed by a role-specific training program is the most efficient way to go about training. This will prevent people from having to attend training sessions that don’t pertain to them.
Phase 4: Implement: Once everything is in place, it’s time to roll out the new maintenance planning and scheduling processes. The goal here is to embed the new standards and procedures into the daily routines of all those involved until they become the new normal. It’s generally accepted to allow for a three-month coaching period, where individuals are assessed and receive help to close any gaps in performance. If you operate a shift system, six months should be sufficient. Remember, planners should only work on the processes, not in the processes.
Phase 5: Review: This is sometimes called the “close-out” phase. Here, you want to ensure the new maintenance planning and scheduling process won’t disintegrate when the training and one-on-one time is over.
Celebrate successes and make sure people are aware of how their hard work is paying off.
Review what is going well and what could be better, and document these for the next meeting with the planning department.
Develop sustainable procedures.
Phase 6: Sustain: This phase is considered “evergreen,” as processes and procedures should always be improving. Be sure you have:
- All performance metrics in place and review them in meetings, verifying that they are meeting long-term trends.
- Clearly defined procedures or job plans for each technician performing certain tasks.
- Ensure new technicians are properly trained on these job plans.
- Standardized, up-to-date and easily accessibly documentation in place.
- A set time for conducting process reviews to assess what is working and what isn’t. This is also the time to go over how processes can be improved.
The term equipment reliability and maintenance (ERM) encompasses not only equipment, such as machines, tools, and fixtures, but also the technical, operational, and management activities, ranging from equipment specifications to daily operation and maintenance, required to sustain the performance of manufacturing equipment throughout its useful life.
Reliability is a special attribute that describes the dependability of a component. This means that the component consistently performs a desired function under certain conditions for a certain period of time in order to meet business goals and customer needs. Theoretically, reliability can be described as:
Reliability = 1 – Probability of Failure
ERM affects drastically the three key elements of competitiveness quality, cost, and product lead time. Well-maintained machines hold tolerances better, help to reduce scrap and rework, and raise part consistency and quality. By increasing uptime and yields of good parts, ERM can reduce capital requirements, thereby cutting total production costs. It also can shorten lead times by reducing downtime and the need for retooling.
The replacement and displacement of conventional electro-mechanical factory equipment by mechatronic equipment have given rise to a very different set of reliability and maintenance requirements. The recent rush to embrace computer-integrated manufacturing (CIM) has further increased the use of relatively unknown and untested technology. The factory is becoming a web of interdependent subsystems, interconnected by computer controllers that communicate horizontally across peer processes and vertically to supervisory controllers above or slaves below. Much of the controller software was written with the assumption that all equipment works properly when, in fact, complicated and unpredictable failure modes, unanticipated by the system and equipment designers, are becoming increasingly apparent. It is seldom possible to predict how a system will fail when something somewhere in the plant breaks down. Because causal relationships are frequently hidden, repair is often time-consuming, expensive, and tedious. A better job of debugging these systems via simulation, analysis, and rapid development needs to be done.
Methods to Ensure Reliability of Equipment
Besides the engineering practices described above, there are three other essential components to equipment reliability: maintenance, inspection, and technology.
Maintenance can be divided into three categories, preventive, predictive, and corrective maintenance. Preventive measures are taken to eliminate unnecessary inspection and repair tasks. Predictive maintenance generally involves nondestructive inspection techniques to monitor the serviceability of the equipment. Corrective maintenance involves repairing or replacing components to restore equipment back to its operating conditions. Collectively, these tasks should be managed in a well developed reliability centered maintenance program.
Nondestructive testing (NDT) techniques are used extensively throughout the lifecycle of equipment to locate and monitor damage mechanisms. Furthermore, inspection plays a major role in any equipment reliability program. Some common NDT methods used in the petroleum and chemicals industries include radiographic testing, ultrasonic testing, electromagnetic testing, and many more. When selecting an NDT method several considerations should be taken into account including the type of damage, where the damage is located (external or internal), and the size, shape, and orientation of the damage.
Additionally, there are two other types of inspection that provide information on the reliability and remaining life of equipment. These include risk-based inspection (RBI) and fitness-for-service (FFS) assessments. Put simply, the purpose of RBI is to identify and understand risk in order to reduce uncertainty about the condition of equipment. FFS assessments are performed to determine if a component is suitable for continued service.
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